This invention relates to a fluid operable mechanism and is particularly concerned with a pneumatic/hydraulic convertor in which a supply of a gaseous medium under pressure is used to generate pressure in and control the application of a liquid medium.
It has for many years been common practice in very many industrial applications to use fluid power operated motors to move machine parts particularly where similar repeated operations are necessary. Broadly such motors have been pneumatic or hydraulic.
Most factories are equipped with the necessary machinery to provide throughout the premises a continuous supply of compressed air which can easily be piped to individual machines. Pneumatic motors are comparatively simple, trouble free and inexpensive to install and use an are entirely satisfactory in many circumstances. However they do suffer from a number of well-known disadvantages which preclude their use for many applications. The most important disadvantages are firstly that because air is elastic it is difficult to achieve precise control and in view of the low pressures involved large displacement volumes are required so that actuators become bulky. Hydraulic motors on the other hand offer very precise control at the point of use and can operate at very high pressure so that large forces can be exerted with the displacement of small quantities of liquid. However the pumping equipment on associated apparatus for hydraulic motor installations is bulky, complex and costly and the fact that the operating medium is substantially incompressible introduces difficulties which add to the costs of the installation.
Many proposals have been made for combining pneumatic and hydraulic systems to take advantage of those features of each system which are best suited to perform particular functions. It is thus known to provide a hydraulic actuator at the point of use and to power this pneumatically.